A Divide and Conquer State Grouping Method for Bitmap Based Transition Compression

Abstract

Member State Bitmask Technique (MSBT) is a hardware oriented transition compression technique which can compress the redundant transitions in a finite automaton. While the compressed automaton is stored in on-chip memories; a dedicated hardware accelerator performs signature matching by comparing the network streams against the compressed automaton at line rate. The MSBT consists of three functional steps which include the intra-state transition compression, state grouping and the inter-state transition compression. The state grouping algorithm which is currently used in MSBT is not compression aware and results in sub-optimal transition compression. To address this weakness, a compression aware Divide and Conquer state grouping method is proposed in this paper, which can efficiently group states that improves the transition compression in MSBT. Experimental evaluation of the proposed state grouping method, results in a reduced on-chip memory usage of the order of 10-30%. The reduction in the memory usage allows to accommodate more signatures in on-chip memories and perform signature matching with them at line rate.